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AJvYcCWUrc+KGJqCvaMsiIhT86ZDwhAy1mNLz/QOh7D0pO1z8zWIwIYBsprLKY3yYLFM98LJme61bPct3VGCZag=@vger.kernel.org X-Gm-Message-State: AOJu0YwtJHSN/HLVBmvHKx2CsmoR+50uE4Rc6v7Vy7dx7VphgKKxqp4j 5SXj+rApgETOhsShHdmr7I+z4bpQb60l5zIz+QTab9fEAf0evjvwFyK9gtlRrIXVFciECwndZFn iMp1oI7NgNlOMvn78Lg== X-Received: from pgcn13.prod.google.com ([2002:a63:720d:0:b0:c73:fb05:a2e3]) (user=guanyulin job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:6a13:b0:39b:da83:91aa with SMTP id adf61e73a8af0-39ef774f7ccmr3683797637.51.1775046768964; Wed, 01 Apr 2026 05:32:48 -0700 (PDT) Date: Wed, 1 Apr 2026 12:32:17 +0000 In-Reply-To: <20260401123238.3790062-1-guanyulin@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260401123238.3790062-1-guanyulin@google.com> X-Mailer: git-send-email 2.53.0.1118.gaef5881109-goog Message-ID: <20260401123238.3790062-2-guanyulin@google.com> Subject: [PATCH v4 1/2] usb: core: use dedicated spinlock for offload state From: Guan-Yu Lin To: gregkh@linuxfoundation.org, mathias.nyman@intel.com, perex@perex.cz, dominique.martinet@atmark-techno.com, eadavis@qq.com, hannelotta@gmail.com, tiwai@suse.com, quic_wcheng@quicinc.com, broonie@kernel.org, arnd@arndb.de, xiaopei01@kylinos.cn, wesley.cheng@oss.qualcomm.com, sakari.ailus@linux.intel.com, stern@rowland.harvard.edu, amardeep.rai@intel.com, xu.yang_2@nxp.com, andriy.shevchenko@linux.intel.com, nkapron@google.com Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-sound@vger.kernel.org, Guan-Yu Lin , stable@vger.kernel.org, Hailong Liu Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Replace the coarse USB device lock with a dedicated offload_lock spinlock to reduce contention during offload operations. Use offload_pm_locked to synchronize with PM transitions and replace the legacy offload_at_suspend flag. Optimize usb_offload_get/put by switching from auto-resume/suspend to pm_runtime_get_if_active(). This ensures offload state is only modified when the device is already active, avoiding unnecessary power transitions. Cc: stable@vger.kernel.org Fixes: ef82a4803aab ("xhci: sideband: add api to trace sideband usage") Signed-off-by: Guan-Yu Lin Tested-by: Hailong Liu --- drivers/usb/core/driver.c | 23 ++++--- drivers/usb/core/offload.c | 102 ++++++++++++++++++------------- drivers/usb/core/usb.c | 1 + drivers/usb/host/xhci-sideband.c | 4 +- include/linux/usb.h | 10 ++- 5 files changed, 84 insertions(+), 56 deletions(-) diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c index d29edc7c616a..74b8bdc27dbf 100644 --- a/drivers/usb/core/driver.c +++ b/drivers/usb/core/driver.c @@ -1415,14 +1415,16 @@ static int usb_suspend_both(struct usb_device *udev= , pm_message_t msg) int status =3D 0; int i =3D 0, n =3D 0; struct usb_interface *intf; + bool offload_active =3D false; =20 if (udev->state =3D=3D USB_STATE_NOTATTACHED || udev->state =3D=3D USB_STATE_SUSPENDED) goto done; =20 + usb_offload_set_pm_locked(udev, true); if (msg.event =3D=3D PM_EVENT_SUSPEND && usb_offload_check(udev)) { dev_dbg(&udev->dev, "device offloaded, skip suspend.\n"); - udev->offload_at_suspend =3D 1; + offload_active =3D true; } =20 /* Suspend all the interfaces and then udev itself */ @@ -1436,8 +1438,7 @@ static int usb_suspend_both(struct usb_device *udev, = pm_message_t msg) * interrupt urbs, allowing interrupt events to be * handled during system suspend. */ - if (udev->offload_at_suspend && - intf->needs_remote_wakeup) { + if (offload_active && intf->needs_remote_wakeup) { dev_dbg(&intf->dev, "device offloaded, skip suspend.\n"); continue; @@ -1452,7 +1453,7 @@ static int usb_suspend_both(struct usb_device *udev, = pm_message_t msg) } } if (status =3D=3D 0) { - if (!udev->offload_at_suspend) + if (!offload_active) status =3D usb_suspend_device(udev, msg); =20 /* @@ -1498,7 +1499,7 @@ static int usb_suspend_both(struct usb_device *udev, = pm_message_t msg) */ } else { udev->can_submit =3D 0; - if (!udev->offload_at_suspend) { + if (!offload_active) { for (i =3D 0; i < 16; ++i) { usb_hcd_flush_endpoint(udev, udev->ep_out[i]); usb_hcd_flush_endpoint(udev, udev->ep_in[i]); @@ -1507,6 +1508,8 @@ static int usb_suspend_both(struct usb_device *udev, = pm_message_t msg) } =20 done: + if (status !=3D 0) + usb_offload_set_pm_locked(udev, false); dev_vdbg(&udev->dev, "%s: status %d\n", __func__, status); return status; } @@ -1536,16 +1539,19 @@ static int usb_resume_both(struct usb_device *udev,= pm_message_t msg) int status =3D 0; int i; struct usb_interface *intf; + bool offload_active =3D false; =20 if (udev->state =3D=3D USB_STATE_NOTATTACHED) { status =3D -ENODEV; goto done; } udev->can_submit =3D 1; + if (msg.event =3D=3D PM_EVENT_RESUME) + offload_active =3D usb_offload_check(udev); =20 /* Resume the device */ if (udev->state =3D=3D USB_STATE_SUSPENDED || udev->reset_resume) { - if (!udev->offload_at_suspend) + if (!offload_active) status =3D usb_resume_device(udev, msg); else dev_dbg(&udev->dev, @@ -1562,8 +1568,7 @@ static int usb_resume_both(struct usb_device *udev, p= m_message_t msg) * pending interrupt urbs, allowing interrupt events * to be handled during system suspend. */ - if (udev->offload_at_suspend && - intf->needs_remote_wakeup) { + if (offload_active && intf->needs_remote_wakeup) { dev_dbg(&intf->dev, "device offloaded, skip resume.\n"); continue; @@ -1572,11 +1577,11 @@ static int usb_resume_both(struct usb_device *udev,= pm_message_t msg) udev->reset_resume); } } - udev->offload_at_suspend =3D 0; usb_mark_last_busy(udev); =20 done: dev_vdbg(&udev->dev, "%s: status %d\n", __func__, status); + usb_offload_set_pm_locked(udev, false); if (!status) udev->reset_resume =3D 0; return status; diff --git a/drivers/usb/core/offload.c b/drivers/usb/core/offload.c index 7c699f1b8d2b..9db3cfedd29c 100644 --- a/drivers/usb/core/offload.c +++ b/drivers/usb/core/offload.c @@ -25,33 +25,30 @@ */ int usb_offload_get(struct usb_device *udev) { - int ret; + int ret =3D 0; =20 - usb_lock_device(udev); - if (udev->state =3D=3D USB_STATE_NOTATTACHED) { - usb_unlock_device(udev); + if (!usb_get_dev(udev)) return -ENODEV; - } =20 - if (udev->state =3D=3D USB_STATE_SUSPENDED || - udev->offload_at_suspend) { - usb_unlock_device(udev); - return -EBUSY; + if (pm_runtime_get_if_active(&udev->dev) !=3D 1) { + ret =3D -EBUSY; + goto err_rpm; } =20 - /* - * offload_usage could only be modified when the device is active, since - * it will alter the suspend flow of the device. - */ - ret =3D usb_autoresume_device(udev); - if (ret < 0) { - usb_unlock_device(udev); - return ret; + spin_lock(&udev->offload_lock); + + if (udev->offload_pm_locked) { + ret =3D -EAGAIN; + goto err; } =20 udev->offload_usage++; - usb_autosuspend_device(udev); - usb_unlock_device(udev); + +err: + spin_unlock(&udev->offload_lock); + pm_runtime_put_autosuspend(&udev->dev); +err_rpm: + usb_put_dev(udev); =20 return ret; } @@ -69,35 +66,32 @@ EXPORT_SYMBOL_GPL(usb_offload_get); */ int usb_offload_put(struct usb_device *udev) { - int ret; + int ret =3D 0; =20 - usb_lock_device(udev); - if (udev->state =3D=3D USB_STATE_NOTATTACHED) { - usb_unlock_device(udev); + if (!usb_get_dev(udev)) return -ENODEV; - } =20 - if (udev->state =3D=3D USB_STATE_SUSPENDED || - udev->offload_at_suspend) { - usb_unlock_device(udev); - return -EBUSY; + if (pm_runtime_get_if_active(&udev->dev) !=3D 1) { + ret =3D -EBUSY; + goto err_rpm; } =20 - /* - * offload_usage could only be modified when the device is active, since - * it will alter the suspend flow of the device. - */ - ret =3D usb_autoresume_device(udev); - if (ret < 0) { - usb_unlock_device(udev); - return ret; + spin_lock(&udev->offload_lock); + + if (udev->offload_pm_locked) { + ret =3D -EAGAIN; + goto err; } =20 /* Drop the count when it wasn't 0, ignore the operation otherwise. */ if (udev->offload_usage) udev->offload_usage--; - usb_autosuspend_device(udev); - usb_unlock_device(udev); + +err: + spin_unlock(&udev->offload_lock); + pm_runtime_put_autosuspend(&udev->dev); +err_rpm: + usb_put_dev(udev); =20 return ret; } @@ -112,25 +106,47 @@ EXPORT_SYMBOL_GPL(usb_offload_put); * management. * * The caller must hold @udev's device lock. In addition, the caller should - * ensure downstream usb devices are all either suspended or marked as - * "offload_at_suspend" to ensure the correctness of the return value. + * ensure the device itself and the downstream usb devices are all marked = as + * "offload_pm_locked" to ensure the correctness of the return value. * * Returns true on any offload activity, false otherwise. */ bool usb_offload_check(struct usb_device *udev) __must_hold(&udev->dev->mu= tex) { struct usb_device *child; - bool active; + bool active =3D false; int port1; =20 + if (udev->offload_usage) + return true; + usb_hub_for_each_child(udev, port1, child) { usb_lock_device(child); active =3D usb_offload_check(child); usb_unlock_device(child); + if (active) - return true; + break; } =20 - return !!udev->offload_usage; + return active; } EXPORT_SYMBOL_GPL(usb_offload_check); + +/** + * usb_offload_set_pm_locked - set the PM lock state of a USB device + * @udev: the USB device to modify + * @locked: the new lock state + * + * Setting @locked to true prevents offload_usage from being modified. This + * ensures that offload activities cannot be started or stopped during cri= tical + * power management transitions, maintaining a stable state for the durati= on + * of the transition. + */ +void usb_offload_set_pm_locked(struct usb_device *udev, bool locked) +{ + spin_lock(&udev->offload_lock); + udev->offload_pm_locked =3D locked; + spin_unlock(&udev->offload_lock); +} +EXPORT_SYMBOL_GPL(usb_offload_set_pm_locked); diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c index e740f7852bcd..8f7ca084010f 100644 --- a/drivers/usb/core/usb.c +++ b/drivers/usb/core/usb.c @@ -671,6 +671,7 @@ struct usb_device *usb_alloc_dev(struct usb_device *par= ent, set_dev_node(&dev->dev, dev_to_node(bus->sysdev)); dev->state =3D USB_STATE_ATTACHED; dev->lpm_disable_count =3D 1; + spin_lock_init(&dev->offload_lock); dev->offload_usage =3D 0; atomic_set(&dev->urbnum, 0); =20 diff --git a/drivers/usb/host/xhci-sideband.c b/drivers/usb/host/xhci-sideb= and.c index 2bd77255032b..1ddb64b0a48e 100644 --- a/drivers/usb/host/xhci-sideband.c +++ b/drivers/usb/host/xhci-sideband.c @@ -291,8 +291,8 @@ EXPORT_SYMBOL_GPL(xhci_sideband_get_event_buffer); * Allow other drivers, such as usb controller driver, to check if there a= re * any sideband activity on the host controller. This information could be= used * for power management or other forms of resource management. The caller = should - * ensure downstream usb devices are all either suspended or marked as - * "offload_at_suspend" to ensure the correctness of the return value. + * ensure downstream usb devices are all marked as "offload_pm_locked" to = ensure + * the correctness of the return value. * * Returns true on any active sideband existence, false otherwise. */ diff --git a/include/linux/usb.h b/include/linux/usb.h index fbfcc70b07fb..a4b031196da3 100644 --- a/include/linux/usb.h +++ b/include/linux/usb.h @@ -21,6 +21,7 @@ #include /* for struct completion */ #include /* for current && schedule_timeout */ #include /* for struct mutex */ +#include /* for spinlock_t */ #include /* for runtime PM */ =20 struct usb_device; @@ -636,8 +637,9 @@ struct usb3_lpm_parameters { * @do_remote_wakeup: remote wakeup should be enabled * @reset_resume: needs reset instead of resume * @port_is_suspended: the upstream port is suspended (L2 or U3) - * @offload_at_suspend: offload activities during suspend is enabled. + * @offload_pm_locked: prevents offload_usage changes during PM transition= s. * @offload_usage: number of offload activities happening on this usb devi= ce. + * @offload_lock: protects offload_usage and offload_pm_locked * @slot_id: Slot ID assigned by xHCI * @l1_params: best effor service latency for USB2 L1 LPM state, and L1 ti= meout. * @u1_params: exit latencies for USB3 U1 LPM state, and hub-initiated tim= eout. @@ -726,8 +728,9 @@ struct usb_device { unsigned do_remote_wakeup:1; unsigned reset_resume:1; unsigned port_is_suspended:1; - unsigned offload_at_suspend:1; + unsigned offload_pm_locked:1; int offload_usage; + spinlock_t offload_lock; enum usb_link_tunnel_mode tunnel_mode; struct device_link *usb4_link; =20 @@ -849,6 +852,7 @@ static inline void usb_mark_last_busy(struct usb_device= *udev) int usb_offload_get(struct usb_device *udev); int usb_offload_put(struct usb_device *udev); bool usb_offload_check(struct usb_device *udev); +void usb_offload_set_pm_locked(struct usb_device *udev, bool locked); #else =20 static inline int usb_offload_get(struct usb_device *udev) @@ -857,6 +861,8 @@ static inline int usb_offload_put(struct usb_device *ud= ev) { return 0; } static inline bool usb_offload_check(struct usb_device *udev) { return false; } +static inline void usb_offload_set_pm_locked(struct usb_device *udev, bool= locked) +{ } #endif =20 extern int usb_disable_lpm(struct usb_device *udev); --=20 2.53.0.1018.g2bb0e51243-goog